In prior art capsule filling machines of the rotary turret type, currently used for filling capsules with doses of pharmaceutical material in powder or particulate form, the capsule weight is monitored in several ways, one of these being a statistical sampling method whereby defined quantities of sample capsules are taken at the outfeed end of the machine at defined time intervals and weighed on precision balances.
According to this method, which is manual and carried out outside the capsule filling machine, if a significant percentage of the sampled capsules are found to be unsatisfactory in terms of weight or do not fall within specified ranges of values, the operator in charge of testing operations must act directly on the capsule filling machine, modifying the dosing parameters of the unit that feeds and doses the pharmaceutical material.
In another method, known for example from European Patent EP 886765 B1, all the capsules made by the capsule filling machine, or a specified quantity of capsules, are fed into the hopper of a weighing apparatus located outside the capsule filing machine and connected to the capsule filing machine by suitable conveying means. This weighing apparatus comprises a rotating suction drum which is mounted under the hopper and which feeds the capsules in single file to a series of weighing heads followed by a conveyor chute with twin outfeed end.
The unit that controls the weighing apparatus receives and processes the signals from the weighing heads to derive the capsule weights and accordingly activates a deflection plate on the twin-outfeed chute so that unsatisfactory capsules are channelled into the outfeed portion of the chute connected to the reject container, while the satisfactory capsules are channelled into the other outfeed portion of the chute connected by suitable conveying means to a packaging machine downstream, for example, a blister packer. Even this apparatus, however, does not eliminate the need for manual operations. Thus, in this case too, if a significant percentage of the capsules are found to be unsatisfactory in terms of weight or do not fall within specified ranges of values, the operator must act directly on the capsule filling machine to adjust the dosing parameters of the system that feeds and doses the pharmaceutical material.
Besides the inconvenience of having to operate manually, outside the capsule filling machine to adjust the pharmaceutical material feeding and dosing system when significant percentages of the capsules are found to have an incorrect weight, there is also the disadvantage that the above mentioned prior art methods do not permit the measurement of other chemico-physical properties of the capsules, for example, the moisture content of the pharmaceutical material inside the capsules, which have a considerable influence on the weight of the capsules themselves.